In conjunction with many electrical converter devices, e.g. a frequency converter, an inductive electrical component is needed between an inverter bridge arranged to produce e.g. multiphase alternating voltage and an electrical system connected to it, and/or between a rectifier bridge and an alternating voltage network. The inductive electrical component can be needed, for example, for reducing slew rate of output voltage of an inverter, for over-current protection, for reducing radio frequency emissions, and/or for suppressing harmonics of voltage and/or of electrical current. The physical size of an inductive electrical component can be reduced by providing the inductive electrical component with a magnetic core element that is made of magnetically amplifying material, i.e. material having the relative permeability greater than unity (μr>1). The magnetically amplifying material can be ferromagnetic or paramagnetic material. The magnetic core element is preferably made of soft magnetic material that provides low hysteresis losses, e.g. electrical steel sheets, soft magnetic powder, ferrites, etc. In many applications, the magnetic saturation of magnetically amplifying material causes problems in conjunction with inductive electrical components, e.g. non-linear phenomena that may be harmful in operation of an inductive electrical component. For example, dynamical inductance (a change of magnetic flux/a change of electrical current) may drastically diminish as a response to a situation in which a magnetic core element of an inductive electrical component gets magnetically saturated. Because of the above-mentioned facts, a magnetic core element of an inductive electrical component is traditionally dimensioned with respect to a pre-determined value of electrical current in such a way that the magnetic core element does not get too deeply saturated during operation. The requirement that the magnetic core element must not get too deeply saturated sets lower limits to the size and the weight of the inductive electrical component.
In a solution according to the prior art, an inductive electrical component that is used for limiting fluctuations of direct electrical current, i.e. dc-current, is provided with a permanent magnet. In this document dc-current means electrical current the value of which may fluctuate over time but the flowing direction of which does not change. The permanent magnet is arranged to generate into a ferromagnetic core of the inductive electrical component a biasing magnetic flux component that has an opposite direction with respect to a magnetic flux component generated by dc-current flowing in windings of the inductive electrical component. With the aid of the biasing magnetic flux component the maximum value of the dc-current that can be used without causing a too deep saturation of the ferromagnetic core can be e.g. doubled compared with a situation in which no biasing magnetic flux component is being used. An inductive electrical component of the kind described above is disclosed also in publication U.S. Pat. No. 3,968,465. The above-described solution according to the prior art is, however, suitable for only inductive electrical components that are used for limiting fluctuations of dc-current. In conjunction with an electrical converter device, e.g. a frequency converter, many inductive electrical components are, however, used as reactors for alternating electrical currents.